Fanatic

A fanatic threw a bomb at the king's coach.

Tom is a fitness fanatic.

He's a bread baking fanatic.

He's a science fiction fanatic.

She's a fanatic.

He's a fanatic.

I'm a fanatic of ecology.

I am a fanatic of ecology.

Tom is a fanatic.

Tom was a desperate fanatic.

But Faith, fanatic Faith, once wedded fast / To some dear falsehood, hugs it to the last.

The reclusive tycoon calling himself the Illusive Man is a human nationalist focused on advancing human interests, whatever the cost to non-humans. The Citadel Council regards him as a fanatic posing a serious threat to galactic security.

A zealot can't change his mind. A fanatic can't change his mind and won't change the subject. —Winston Churchill (attributed)

A fanatic is one who redoubles his effort when he has forgotten his aim. —George Santayana